#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main() {
    double a, b, c, e, d;
    scanf("%lf %lf %lf %lf %lf", &a, &b, &c, &d, &e);
    printf("%.2f", (a + b + c + d + e) / 5.0);
    return 0;
}